A Drink A Day Tied To Increased Breast Cancer Risk, New Report Says

The researchers reviewed 112 different studies from around the world.

Researchers have long known that having one too many cocktails might be associated with an increased risk of breast cancer.

Now, a new report from the World Cancer Research Fund and the American Institute for Cancer Research reveals just how much of a risk daily drinking might pose for both premenopausal and postmenopausal women.

Sipping an average of 10 grams of alcohol a day—equivalent to a small glass of wine, an 8-ounce beer or 1 ounce of hard liquor—is associated with a 5% increased breast cancer risk in premenopausal women and 9% increase in postmenopausal women, said Dr. Anne McTiernan, a lead author of the new report and a cancer prevention researcher at the Fred Hutchinson Cancer Research Center in Seattle.

“I was most surprised by the alcohol result, that risk increases at just one drink a day, on average,” McTiernan said. “The increase with one drink a day was small … but the risk goes up from there. So that’s why AICR recommends no more than one alcohol drink a day for women to reduce risk for cancer.”

Globally, breast cancer is the top cancer in women, in both the developed and developing worlds, according to the World Health Organization.

In the United States and the United Kingdom, about 12% of women will develop breast cancer at some point in their lifetimes, according to the National Cancer Institute and the organization Cancer Research UK.

For the new report, researchers analyzed 119 observational studies on breast cancer risk from around the world. Those studies included 12 million women total and more than 260,000 cases of breast cancer.

Although breast cancer can occur in men, it is rare—accounting for less than 1% of cancer incidence—and such cases were not included in the report.

When analyzing associations specifically between breast cancer risk and alcohol use, “the premenopausal analysis included 10 large cohort studies in which over 4,000 women developed breast cancer,” McTiernan said. “The postmenopausal analysis included 22 large cohort studies in which over 35,000 women developed breast cancer.”

There are a number of possible explanations for the link between alcohol consumption and breast cancer risk, said Chin-Yo Lin, a researcher at the University of Houston’s Center for Nuclear Receptors and Cell Signaling, who was not involved in the new report.

For instance, “in exposed tissues, alcohol is converted into acetaldehyde, a chemical that can cause mutations in DNA, which can potentially lead to cancer,” Lin said.

“Alcohol consumption is also associated with elevated levels of the female sex hormone estrogen. Excessive cumulative exposure to estrogen is a major risk factor in breast cancer,” he said. “A number of studies have shown that alcohol can enhance the actions of estrogen in breast cancer cells.”

Lin led one study, published in the journal PLOS ONE in 2015, that showed that alcohol may increase the growth of breast cancer cells by influencing a specific gene called BRAF.

The study involved examining how alcohol affects estrogen receptor-positive breast cancer cells. In other words, these are the cancer cells that bind estrogen, which helps them grow.

Lin and his colleagues found that since alcohol promotes the expression of BRAF, this might allow the cells to grow even faster in the presence of estrogen.

Yet, as part of an ongoing debate, “it should be noted that light drinking appears to protect against heart disease,” Lin said. “Those beneficial effects should be weighed against the slight increase in risk for breast cancer.”